


Undersidious

by orphan_account



Series: Undersidious [1]
Category: Undertale (Video Game)
Genre: Cliffhangers, Determination (Undertale), F/F, Gen, Gender-Neutral Frisk, I Don't Even Know, Limited Resets, Mystery, Resets, all humans can reset, more tags, undyne is sad, who killed frisk
Language: English
Status: Completed
Published: 2017-04-23
Updated: 2017-04-23
Packaged: 2018-10-23 02:41:34
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings, Major Character Death
Chapters: 3
Words: 3,203
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10710489
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: So insidious means proceeding in a gradual, subtle way, but with harmful effects. Take that, now apply it to Undertale. That's pretty much what this is.





	1. Arc 1 Chapter 1

**Arc 1 Chapter 1**

 

Every human can reset. This accounts for loading and whole-life resets. However, most only have one or two. Few still have theirs come adulthood. Very, very few have more than ten. Yet, there are some people, the ones with the most determination that seem to have limitless resets. Having over a thousand resets in their arsenal. These people are highly sought after, so any person with a Reset Count -- this is found on the back of the left hand -- over fifty must be separated from the rest of society.

 

***

 

This is the 134th reset. The number 867 is present on Frisk's hand in bright red. They're getting bored of doing the same old thing. What if, they wonder, they went through and actively killed everything? What would the result be then? They grin. They had been getting bored of going through and getting killed that many times over and over just for them to be fickle and become their friend in the end.

 

And so that's what they did.

 

And getting blasted at by whatever those things were that Sans has, hurts.

 

***

 

They're doing that again however. It was fun. They enjoyed it. They'll stop at some point.

 

***

 

220 glows red and drops to 219, and Frisk finds themself in the Ruins again. Now, they can be a pacifist and get their happy ending. But something was different. They could tell.

 

And they found out what during their fight with Undyne. She had thrown two spears when their health was getting pretty low, and they had to load. When they did, the wounds remained. They don't feel any pain, but the blood is freely flowing down and staining their sweater. They take a minute to wonder if it's a side effect of resetting too many times. Is their determination lessening? Possibly.

 

Not wanting to really test that theory, they are careful to stay as uninjured as possible for the rest of their run. Which was pretty hard considering they had to fight Omega Flowey because they forget to befriend Undyne and Asriel because that's just how a pacifist run works.

 

Having only eight resets left, they decide not to even consider another run.

 

*** Undersidious ***

 

They're asleep. Finally. He sneaks into the room and looks at the infinitely bleeding child. He's sure they're only still alive because of their sheer determination. He sighs. He'll need to kill Frisk eight times before they really die. Or is it nine? He's still confused about the whole deal. Frisk had explained it to him once; he won't lie about the fact that he didn't know what half of the words they used meant.

 

He summons his preferred weapon and attacks. They load, and he's back where he was when they last loaded. This will take a while.

 

***

 

Over the course of nine years, Frisk is seventeen and only has one reset remaining. They're confused on why their last save is loaded right as they fall asleep some nights. However, tonight, they are going to have a talk with everybody they have told. Which is Sans, Asgore, Toriel, and Alphys. They didn't tell Papyrus and Undyne because Papyrus is too innocent and would feel bad. And Undyne because the ones that are from her spears are very obvious, and they wouldn't want Undyne to feel guilty with the reminder of what she did.

 

***

 

"My Reset Count has been dropping over the years from when I freed the monsters to now. At this point, I have only one remaining," Frisk shows it to them to make a point. Everybody looks surprised.

 

Frisk doesn't give anyone time to make any sort of interruptions, "All of you have a reason for wanting me dead, but if my gut feeling is right, and it is, only one of you have done it. Let's start with you, Mom."

 

Toriel has an expression of confusion and surprise.

 

"Mom," Frisk starts professionally, "you're still worried that I'm going to undo everything, and you love me so much and want me to grow up properly. This is a story of a loving mother willing to go to any lengths to make sure her child can live with her."

 

Toriel looks slightly guilty, not necessarily because she did but because what was said was partly true. She would go to nearly any length to keep Frisk safe.

 

"Now, Dad, you're my next suspect," Frisk accuses, turning to face the king. "You're still worried that I'll go back and kill everybody. You just want to keep everyone safe, so to do that, you lowered my Reset Count to one. That way, I wouldn't make any risky moves because I'd surely die along the way if I tried such a thing. This is the story of a king who wants to protect his people."

 

Asgore looks guilty, not necessarily because he did it but because what was said was partly true. He is still a little wary after being told of the ability, and he just wants to keep his people safe.

 

"Next, we have Alphys," Frisk turns to her. "It could be that you feel that Undyne knows these injuries are from her spears and feels really guilty about it, and you just want her to be happy. So, you're lowering my Reset Count. This is a story of a girl in love with her girlfriend and willing to do anything to keep her happy."

 

Alphys is a blushing mess and as well looks a bit guilty. Admittedly, she does get the feeling that Undyne knows. Despite her brash decisions and cooking style, she's a smart woman. She can put two and two together and get a result.

 

"And Sans. You're the most qualified to have done this. You know why," Frisk finishes off simply.

 

The others are looking at Sans like he spontaneously exploded into alien kittens. Confusion, surprise, and a little awe. Sans just continues not to make eye contact. That's nothing new though.

 

"S-so if we're a-all valid candidates who, uh, do you think did it?" Alphys finally speaks up, breaking the slowly forming awkward silence.

 

"by deciding who it's not," Sans says as if it's the most obvious thing.

 

"Precisely," Frisk agrees with his claim. There's a silence that follows.

 

"My child, how can you be for sure who it was or wasn't?" Toriel asks uncertainly.

 

"I know you guys that well. I know what you would or wouldn't do and to what lengths you'd go to do such things. So to make things shorter, my guess is...," Frisk starts and pause for dramatic affect.

 

There's a tense silence as everyone is on edge and shifting nervously, being put on the spot and all. Nobody would want to be called out on attempting to murder the Ambassador of Monsters. Especially if they are all monsters.

 

"None of you."

 

"Huh?"

 


	2. Arc 1 Chapter 2

**Arc 1 Chapter 2**

 

Recap:

 

_"I know you guys that well. I know what you would or wouldn't do and to what lengths you'd go to do such things. So to make things shorter, my guess is…," Frisk starts and pause for dramatic affect._

 

_There's a tense silence as everyone is on edge and shifting nervously, being put on the spot and all. Nobody would want to be called out on attempting to murder the Ambassador of Monsters. Especially if they are all monsters._

 

_"None of you."_

 

_"Huh?_ "

 

_ _ _ _ _ _ _ _

 

"That's right," Frisk tells them. "It was none of you. And I know who it is. I'm going to confront them tonight. They know exactly where I'll be. Don't interfere. Just let it be. I'll handle this."

 

"My child, I can not allow such a thing," Toriel says sternly but with all good intentions.

 

"Mom, I promise I can handle this. Have I ever broken a promise to you?" Frisk asks.

 

Toriel opens her mouth to protest, but she is silenced by the truth of the statement. She is still very much worried about Frisk. Frisk is their child. How can she stand to let her child confront such dangers alone? It leaves her to wonder who the aggressor is.

 

"Are you sure, Frisk?" Asgore asks worriedly. He would hate to have been able to protect them but failed for not trying to change their mind on the matter.

 

"Yes, Dad. I can do it. Nobody will be harmed, and by tomorrow, everything will be back to normal," Frisk assures him.

 

Alphys looks nervously to Sans then to Frisk as she nervously messes with her hands. Sans looks at Alphys with a look that makes her feel slightly less nervous. She nods, trusting Sans' judgement.

 

"you better not be lying," Sans says simply, but so much meaning is carried in just those five words.

 

"You guys have nothing to worry about."

 

***

 

It's the next morning, and Frisk is alive and well. They're assumptions had been correct. However, the reason for the person doing it was off. Way off. They hadn't considered that. Dear King Asgore, the hadn't considered that go be a possibility. Sure, they had somehow gotten to the conclusion as to who it was by chance. And they had somehow been right. However, they never in a million years would have considered that to be his reason for doing this.

 

"kid, is something wrong?" Sans asks, just a little worried.

 

"Yes, it's just… Would you believe me if I told you a monster wanted me dead, and I quote, 'Just for the sake of doing it'?"

 

"a monster? i don't see that happening. so what else did you find out?"

 

"I'll be dead by next week. Or so the threat went. Also…"

 

"'also'?"

 

Frisk holds up their left hand and turns it to show Sans the four red numbers: 0000.

 

"SANS!" is heard from upstairs.

 

"i better check on him. see you later."

 

***

 

Papyrus and Sans had been staying for the holidays. Now, they needed to pack back up for their trip home. The two are pushing and shoving their stuff into their bags. Or Papyrus is rather. Sans is just lying around. He'd do it later.

 

"SANS! WE WILL GET HOME LATE IF YOU DON'T PACK NOW!" Papyrus yells animatedly. It's quite a comical sight and seems like something you'd only see in cartoons. Sans waits a few minutes before relenting and getting to work on getting his stuff into the bag they had came in. All the while, he wonders who the monster is that is attacking Frisk in their sleep, who Frisk confronted last night, and who downed Frisk's last reset.

 

"ok, bro. let's go now," Sans says as he puts in one last shirt.

 

***

 

In her room, Alphys is watching some of Mettaton's old shows such as Cooking With A Killer Robot. They watch Frisk scramble around for the ingredients that are right there on the counter. It's like they were doing it deliberately. Oh. They probably were. It's no fun if they look like that have no clue what they're doing.

 

Undyne barges in and asks, "Hey, Alphys, what're you watching?"

 

"Just s-s-some of Mettaton's shows f-fr-from the Underground."

 

"Awesome! After this, let's watch some anime!"

 

"Okay."

 

***

 

Toriel is baking a butterscotch-cinnamon pie for everyone. Outside, Asgore is watering some flowers in his garden. Frisk is working on their homework. They have just one more problem, and they're good to go.

 

***

 

Three days. It's been three day. Everyone that knows of the situation is super on-edge. Sans is making constant checks on Frisk. Toriel and Asgore are staying up later than usual, just to make sure nobody sneaks in to hurt Frisk. Undyne doesn't know, but she's reassuring Alphys that whatever she's been worried about will be alright. It doesn't do too much to calm her nerves.

 

***

 

Frisk lies in their bed asleep. The murderer appears. The same one that has been killing them over the span of these nine years. However, Frisk lies asleep, unknowing to the threat that looms above them. A smile is clear on his face. Does he need a reason to kill someone? He just does it because he can. Because he wants to do it. He's not bring controlled or manipulated. This is all on him. And he's going to finally kill them for good.

 

He summons his weapon and enjoys the feeling of it being in his hand.  Some may call his preferred weapon inconvenient and ineffective. However, he feels the opposite about it. He can summon it very easily, and it gets the job done just as well as any knife or gun would.

 

The monster considers the good the human has done. Then, he remembers that a majority of their ability was wasted on murdering the innocent. That's not exactly the reason for him doing this, but that was what pushed him over the edge. That thought pushes him on. It makes him want to do something about it.

 

He raises his weapon and slams it down with enough force to instantly shatter Frisk's dull red soul. Forever. Frisk will not be coming back. He will not allow such a thing. Then, just as quickly as he came, he leaves.

 


	3. Arc 1 Chapter 3

**Summary for the Chapter:**

> The funeral and Undyne is a sad.

**Notes for the Chapter:**

> This is the last chapter of the first arc. You finally figure out who the cause of this mess is.

**Arc 1 Chapter 3**

Recap:

 

_He raises his weapon and slams it down with enough force to instantly shatter Frisk's dull red soul. Forever. Frisk will not be coming back. He will not allow such a thing. Then, just as quickly as he came, he leaves._

 

_ _ _ _ _ _ _ _

 

Toriel is sobbing. Asgore is also sad, and he comforts her. Papyrus is also evidently affected by the sudden loss of his favorite human. Sans has mixed emotions and is comforting his brother. Alphys seems pretty upset. Undyne is quite clearly pissed off. She's yelling at Frisk to stay determined. To get up already. She's threatening them. Ordering them. Frisk does nothing. Being dead does that to a person. Sans doesn't say that though.

 

"Please…, I'm begging you, punk. Frisk," Undyne pleads. "Tell me this is a joke. Tell me you got me. Just… I'm not ready to lose you."

 

Now Undyne is collapsed on her knees, sobbing loudly. It's a sad sight to see. Sans wants to comfort her and tell her that he understands, but Alphys seems to be doing that already. Undyne and Frisk had been besties. They always liked to hang out. Now, that'll never happen again.

 

***

 

Undyne is standing out in the rain. She screams angrily. It's loud and full of agony. She's angry at Frisk. She's angry at the world. She's especially angry at whoever it was that killed her bestfriend. Once she gets her hands on that guy, she's going to… going to…

 

She just gets sad. She doesn't want Frisk to have to deal with that guy all over again in the afterlife. Anyways, Frisk wouldn't want her to do this. Frisk would pet the vegetables and put the noodles in one at a time. And now, she's just crying all over again.

 

***

 

Another day, Undyne is yet again visiting Frisk's grave. Undyne yells at the skies.

 

"Take me instead!" "Give Frisk back!" "I'll do anything!" "They have family and friends here!"

 

None of the offers are considered. Undyne yells and looks at the gravestone that just mocks her with their name and the day of death.

 

She whispers, "Punk, listen, I… this isn't working. I've tried my best. Nothing is working. I'm sorry. For everything. Those scars you have, I know those were from my spears. And I just didn't want to believe it."

 

She continues, "You've suffered so much for monsterkind, so thanks a lot for that. Thank you for believing in me. And thanks for being a wimp. And I especially thank you for being my bestie. I haven't cried like this since we watched that one anime with Alphys. You know, the one where they're all dead. Angel something? Yeah."

 

***

 

Again, it's raining outside while Undyne sits it front of the grave, not caring that it's rainy or that the ground is muddy. She's just sitting there, letting Frisk enjoy her company. She just takes this time to silently mourn the loss of her bestfriend.

 

***

 

"undyne has really gotten quiet," Sans points out. It's something all of them have noticed but have neglected to mention. It was like an unspoken rule to not mention the fact. Now, they have to have this conversation.

 

"Y-yeah," Alphys sighs. "Sh-she's g-getting better. Frisk really h-has impacted her life. It m-must be awful. I mean, I miss Frisk, too, b-but…"

 

"We understand," Toriel cuts her off. Alphys smiles.

 

"do you think she's going to stay life that?" Sans inquires.

 

"Perhaps. What are your thought, Dr. Alphys?" Toriel responds.

 

"Um, I-I want to say sh-she might for a little w-while, but I think… she's going to…," Alphys trails off. A silence drifts through and decides to stay for now.

 

***

 

Toriel is cleaning Frisk's room when she sees a paper on their desk addressed to Undyne. She smiles gently. Frisk. She wipes away a few stray tears, "My child, you are still looking out for us. Thank you."

 

Toriel picks up the letter and walks down the hall. She knocks on a door. Alphys opens it. Toriel explains, "I found this in Frisk's room while I was cleaning. Would you give it to Undyne?"

 

"Of course, Toriel!" she accepts.

 

***

 

Dear UnDyne,

 

By the tim3 you get this letTer, I will surely hav3 passed on. I am soRry that you are sad. I am sorry that you are suffering. I wish I could be there for you. I wish I could say a proper goodbye, but I don't know when I'll be gone. You will always be My bestfrIend. Remember that. However, doN't forget to m4ke more friends. Try not to let your anger get the best of you. I won't be there to pacify any conflicTs. Don't forget to be yourself. Be whoever you are. Be my bestfr1end. And be alive. That's all I ask, 0kay, UNdyne?

 

Love,

Frisk.

 

Undyne stares at the paper that is slightly crumpled in her trembling hands. Her tears make it a little hard to read the paper, but she got the message.

 

D E T E R M I N A T I O N

 

***

 

A figure stands before the gravestone. This is the one who has killed Frisk. Anybody who saw this and knew would think he's trying to torture his victim's soul even after death. He is in a way. He has a wide grin on his face. He crouches down and examines the fresh dirt. He places a bouquet of flowers down. It's the least he could do after murdering them. Frisk had still been in high school after all. It would've been rude not to do so. Anyways, he has an image to uphold.

 

He whispers to the gravestone, "So Frisk, how's it like being the one dead for a change when you had done nothing wrong? Do you finally understand? I'm not quite what you thought me to be, was I?"

 

"papyrus, come on. we should get going now," Sans calls from a little bit away.

 

"OKAY!" the figure responds before getting up and leaving the gravesite behind.

 

**Notes for the Chapter:**

> Twist ending, right? Did you see it coming?
> 
> I'll get straight to work on the next arc.


End file.
